double sin(double x) double cos(double x) double exp(double x) 返回e^x double log(double x) double pow(double x,double y) 返回x^y double sqrt(double x) 返回根号下x double fabs(double x) 返回x的绝对值 double ceil(double x) 返回大于或等于x的最小整数(上取整) double floor(double x) 返回小于或等于x的最大整数(下取整) log(x); //返回的是ln(x) log10(x); 返回的是lg(x)